re-creating C++'s reference bahavior

[swiftcoder]

What it really gets down to, is that I don't want to increase the code complexity needlessly. For many reasons, there shouldn't be a copy made when all we want to do is query a member, and we musn't have a copy when we set a member:

float x = n.position.x; // or:
n.position.x = 10;

But we do want a copy when we request the whole vector:

Vector3f v = n.position;

So maybe the best thing is to override opAssign() to copy (thus behaving like a struct). Then the olnly thing to make sure is that functions taking a vector as an 'in' argument make a local copy rather than modifying the argument directly. And since opAdd, etc. already produce new vectors, I don't think that will be much of a problem.

Does this make sense to you?

Derek Parnell Wrote:

> On Mon, 16 Apr 2007 20:47:31 -0400, swiftcoder - Tristam MacDonald wrote:
> 
> > I am fairly new to D, from a C++ background, and I am having a
> > hard time coming up with a sensible way to deal with what is
> > a fairly trivial example in C++:
> > ...
> > But now in D, I find that the last statement requires ...
> 
> Does this below help any?
> 
> ////////////////////
> import std.stdio;
> 
> class Vector3f
> {
>     int x;
>     float y;
> }
> 
> class Node
> {
>     Vector3f m_position;  // (reference to) a Vector
>     Vector3f position()   // Copy-getter
>     {
>         Vector3f t = new Vector3f;
>         // copy fields by hand
>         t.x = m_position.x;
>         t.y = m_position.y;
> 
>         return t;
>     }
> 
>     Vector3f* position_flds() // Reference-getter
>     {
>         return &m_position;
>     }
> 
>     this() { m_position = new Vector3f; }
> }
> 
> void main()
> {
>     Node n = new Node;
> 
>     writefln("A %s %s", n.position.x, n.position.y);
>     n.position_flds.x = 1;
>     n.position_flds.y = 2.2;
>     writefln("B %s %s", n.position.x, n.position.y);
> 
>     Vector3f v = n.position;
>     writefln("C %s %s", v.x, v.y);
>     v.x = 10;
>     v.y = 9.9;
>     writefln("D %s %s", v.x, v.y);
>     writefln("E %s %s", n.position.x, n.position.y);
> }
> ///////////////////
> 
> 
> -- 
> Derek
> (skype: derek.j.parnell)
> Melbourne, Australia
> "Justice for David Hicks!"
> 17/04/2007 5:30:04 PM